"It was a problem. Sometimes I would feel it during the games, it was really hard to breathe for me, but now it's fine."

City have already spent close to £150million this summer on Kyle Walker, Danilo and Benjamin Mendy and the club are likely to pass the £200million-mark before the transfer window closes.

Guardiola's spending spree will increase expectations on his side in the Premier League and particularly the Champions League, where they have reached the semi-finals only once in five consecutive attempts.

Sane says the target is to haul in Real Madrid, who have won the tournament twice in a row and in three of the last four seasons.

Pep Guardiola hopes to see Leroy Sane back to his best (Image: REUTERS)

"They are two-time Champions League winners, so I think it is going to be difficult, but we can do it if we improve a lot and work on our problems," Sane said.

"I don't think we are one of the favourites, but we can go through to the semi-finals. We have a team that can do it, experienced young players who play very well. If we work a lot and improve, we can do it.

"Pep (Guardiola) has won many trophies and he gives us a lot of belief. It is a big year. I want to win some trophies."